The present invention relates to the art of generating alphanumeric characters and other symbols for reproduction by an electro-optical scanner. Such an electro-optical scanner may be a Cathode Ray Tube (CRT) a laser beam scanner or other character imaging device capable of being electronically controlled.
In electro-optical typesetters, characters are commonly stored in digital encoded format. The characters are initially first designed on a fine grid or matrix and then digitally encoded from that matrix.
Encoding the characters on a normalized font is shown in greater detail in patent application U.S. Ser. No. 905,451, filed May 12, 1978, now U.S. Pat. No. 4,199,815 and U.S. patent application Ser. No. 950,242, filed Oct. 10, 1978, now U.S. Pat. No. 4,231,096, both assigned to the common assignee as this application.
A further application assigned to the common assignee and disclosing the manner in which the encoded characters are arranged for use with the electro-optical scanning system is shown in U.S. patent application Ser. No. 097,276, and filed Nov. 26, 1979.
As shown in these prior applications, the Outline is countour encoded by straight lines and the encoding of the straight line vectors start at selected points on the outline. The contiguous vectors, proceeding in a vector profile along the outline, are encoded in a digital format. The outline may start for example with the left most point of the character and proceed around the character ending at the right most point of the character. This scheme would be most preferable in a scanning device where the character was imaged by a scanning beam moving up and down, and the vector outline would be translated into beam intercept points for blanking and unblanking the beam.
The outline vectors can proceed from the top most part of the character outline and then proceed down the character with the vector profiles defining the character terminating at the bottom most point of the character. This encoding scheme would be preferable where the scanning beam is moved across the character for example from left to right and the vector outlines then define intercept points for the character outline, to properly blank and unblank the beam for character imaging.
However, in any character encoding scheme, wherein the code is written for a normalized character, the various encoded angularities formed by contiguous vectors in a outline vector profile when expanded become more pronounced and more discernible to the naked eye when the character is imaged in even larger sized characters.
In these foregoing encoding schemes or in any other contour straight line character encoding scheme, where an attempt is made to simulate a curve with a series of straight line segments, the acceptable expandable limits of the normalized character is limited by angularities in outline profiles.
While each point on the outline can be separately encoded to produce a smooth curve, the cost of such encoding would be significantly higher. Therefore, practical encoding schemes requires this aforesaid simulation of curves using straight line segments which result in insignificant outline angles in a small size character but which result in the angle becoming more and more apparent as the character size is expanded and prevents the full use of the normalized encoded character as a source of varying size characters, especially larger size characters.